averaging in sensor space

Robert Oostenveld r.oostenveld at FCDONDERS.RU.NL
Fri Aug 12 14:10:14 CEST 2005

Hi guys,

Just some additions to Ole's nice arguments...

On 12-aug-2005, at 12:13, Ole Jensen wrote:
> We are often using the following approach
> 1) Calculate time-frequency representations (TFRs) of power for
> planar gradients
> 2) Combined the planar gradient for each orientation
> 3) Average over subjects in sensors space
> 4) Use randomization statistics to identify clusters of difference

Prior to step 1, we would MEGREALIGN the raw data as obtained from
preprocessing to a template helmet location (typically the average
over all subjects in the study). That realigmnent reduces some
variance in the averaging in step 3.

After determining the time-frequency tile of interest (step 4), we go
back to the original data as obtained from PREPROCESSING (i.e. prior
to MEGREALIGN) and repeat FERQANALYSIS with settings (timewindow
+frequency+multitapers) that are tuned to optimize the frequency
estimate in that TF tile. And then we continue with

> 5) Use the beamformer to estimate power in source space for time
> and freq tiles identified in 4) in individual subjects
> 6) Morph the results of beamformed power to a standard brain
> 7) Average morphed power representations in source space


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